The compound bow is generally characterized by the presence of one or more leveraging devices, typically on the distal ends of the bows limbs. The leveraging devices are used to generate a mechanical advantage favoring the archer. As a compound bow is drawn, the force required to displace the bowstring increases rapidly to a maximum value, typically prior to reaching the mid-point of the draw cycle. At some point beyond mid-draw, the force required to displace the bow string an additional amount decreases with each additional increment of displacement. As a result, at full draw the archer is only required to exert a fraction of the maximum force that was required to initially draw the bow.
One of the earliest compound bows is described in U.S. Pat. No. 3,486,495 to Allen. Although Allen discloses the use of programmed cams, such cams did not actually appear in the marketplace until the advent of computer numerically controlled (CNC) machinery made them economically feasible to produce and sell.
With the advent of CNC machinery, the state of the art has progressed from circular cam profiles to programmed non-circular profiles that result in the ability to store more energy in the bow and therefore provide more energy to accelerate an arrow to a higher launch velocity.
Improvements in cam design have been accompanied by advances in the design of the cable rigging. Some of the early compound bows had auxiliary intermediate idler pulleys with their anchor cables adjustably fastened to the handle sections of the bows. Typically, such bows had two cam elements each mounted independently and requiring very meticulous adjustments to each to synchronize the action of the two cam elements to achieve optimum performance.
More recent dual cam bows have been rigged such that the anchor cables of one cam were secured to the axle which mounts the opposite cam. This tied the system together and provided a degree of corrective feedback that made it difficult to detect discrepancies in eccentric wheel synchronization.
Unfortunately, however, with the advent of programmed cams that were capable of storing even more energy, the cam synchronization problem reappeared and the problem increased with increases in energy storage capability combined with progressively lower holding weights.
The background of compound bow development is well documented in the patents that have been granted in this area and for a deeper understanding of the state of the art one can find additional information in the following patents and the patents which they reference:
U.S. Pat. No. Issued To 3,841,295 Hunter 3,854,467 Hofmeister 3,958,551 Ketchum 4,440,142 Simonds 4,838,236 Kudlacek 5,040,520 Nurney 5,307,787 LaBorde et al. 5,368,006 McPherson 5,505,185 Miller 5,678,529 Larson
The innovation of the dual feed-out single take-up single cam compound bow, disclosed in U.S. Pat. No. 5,368,006 provided a major step forward in the simplification of the compound bow.
As may be seen from U.S. Pat. No. 5,368,006 as well as many of the cam equipped bows available today, the feed-outs and take-up portions of most cams consist of grooved tracks which function to provide the bow string with a defined guide path. The various cam assemblies are intended to increase bow efficiency and power. However, it is also desirable to provide a cam with increased efficiency but which will also provide a bow with nock point travel which is smooth and continuous, and which provides for a nock point which remains level throughout the drawing of the bow string.
Recently, attempts have been made to modify the dual feed-out single take-up cam in order to provide for improved performance of the bow, notably by adjusting the structure of the cam to provide for even more efficient energy storing capability as well as to improve the movement of the cam for greater efficiency and quieter performance.
The present invention provides for increased energy storing ability and improved efficiency as well as the desired level nock point which is smooth and continuous throughout the draw, while using a simple pulley on the opposing limb of the bow.
Other inventions which may be utilized with, or which may be otherwise relevant to, the present invention are disclosed in the following concurrently filed and commonly assigned applications: U.S. application entitled BOW VIBRATION DAMPER, application Ser. No. 09/503,013, filed Feb. 11. 2000; U.S. Application entitled IMPROVED ELASTICALLY MOUNTED COUNTER WEIGHT, application Ser. No. 09/502,149, filed Feb. 11, 2000; U.S. application entitled ROUND WHEEL CAM, application Ser. No. 09/502,354, filed Feb. 11, 2000; U.S. Application entitled ARCHERY BOW WITH BOW STRING COPLANAR WITH THE LONGITUDINAL AXIS OF THE BOW HANDLE, application Ser. No. 09/502,917, filed Feb. 11, 2000; and U.S. Application entitled LEVEL NOCKING POINT TRAVEL CAM, application Ser. No. 09/502,152, filed Feb. 11, 2000.
For the purpose of this disclosure, all U.S. patents and patent applications and all other publications referenced herein are incorporated herein by reference in their entirety.